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Data Manipulation (SQL/Python) questions require understanding of core concepts and practice. PracHub provides solutions with explanations to help you master data manipulation (sql/python) interviews.

What difficulty level is this interview question?

This is a Medium difficulty Data Manipulation (SQL/Python) question, commonly asked during Onsite rounds at PayPal.

What role is this question designed for?

This question is commonly asked for Data Scientist candidates at PayPal during technical interviews.

Write conditional aggregates with CASE WHEN

Last updated: Mar 29, 2026

Quick Overview

This question evaluates a candidate's ability to implement conditional aggregation in SQL using CASE WHEN, assessing practical query-writing skills and understanding of conditional expressions for grouped counts and conditional sums.

PayPal

Jul 31, 2025, 12:00 AM

Data Scientist

Onsite

Data Manipulation (SQL/Python)

Write a query that produces conditional aggregates using CASE WHEN (e.g., counts of approved vs declined transactions per merchant and the sum of amounts flagged for review). Explain why CASE WHEN is the portable approach across SQL dialects compared with dialect-specific boolean-to-integer coercion (e.g., SUM(column = 'x')). Discuss readability and maintainability trade-offs.

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